I went through an agency, and had an interview with the operations manager. The interview was pretty standard questions and wasn't difficult at all. I believe I was asked around 4-5 questions. Why the civil service, My skills, Why I would be a good fit for the role etc.

Straightforward interview based around the civil service success profiles. They ask competency based questions and strength based questions. The questions are designed to allow you to demonstrate the various skills and behaviours relevant to the role in your answer.